Single‐Molecule Magnetism,Enhanced Magnetocaloric Effect,and Toroidal Magnetic Moments in a Family of Ln4 Squares

Three cationic [Ln₄] squares (Ln=lanthanide) were isolated as single crystals and their structures solved as [Dy₄(μ₄‐OH)(HL)(H₂L)₃(H₂O)₄]Cl₂?(CH₃OH)₄?(H₂O)₈ ( 1 ), [Tb₄(μ₄‐OH)(HL)(H₂L)₃(MeOH)₄]Cl₂?(CH₃OH)₄?(H₂O)₄ ( 2 ) and [Gd₄(μ₄‐OH)(HL)(H₂L)₃(H₂O)₂(MeOH)₂]Br₂?(CH₃OH)₄?(H₂O)₃ ( 3 ). The structures are described as hydroxo‐centered squares of lanthanide ions, with each edge of the square bridged by a doubly deprotonated H₂L^2? ligand. Alternating current magnetic susceptibility measurements show frequency‐dependent out‐of‐phase signals with two different thermally assisted relaxation processes for 1 , whereas no maxima in χ_M“ appears above 2.0 K for complex 2 . For 1 , the estimated effective energy barrier for these two relaxation processes is 29 and 100 K. Detailed ab initio studies reveal that complex 1 possesses a toroidal magnetic moment. The ab initio calculated anisotropies of the metal ions in complex 1 were employed to simulate the magnetic susceptibility by using the Lines model (POLY_ANISO) and this procedure yields J₁=+0.01 and J₂=?0.01 cm^?1 for 1 as the two distinct exchange interactions between the Dy^III ions. Similar parameters are also obtained for complex 1 (and 2 ) from specific heat measurements. A very weak antiferromagnetic super‐exchange interaction (J₁=?0.043 cm^?1 and g=1.99) is observed between the metal centers in 3 . The magnetocaloric effect (MCE) was estimated by using field‐dependent magnetization and temperature‐dependent heat‐capacity measurements. An excellent agreement is found for the ?ΔS_m values extracted from these two measurements for all three complexes. As expected, 3 shows the largest ?ΔS_m variation (23 J Kg^?1 K^?1) among the three complexes. The negligible magnetic anisotropy of Gd indeed ensures near degeneracy in the (2S+1) ground state microstates, and the weak super‐exchange interaction facilitates dense population of low‐lying excited states, all of which are likely to contribute to the MCE, making complex 3 an attractive candidate for cryogenic refrigeration.     

Inverse Electron Demand Hetero Diels–Alder Reactions of Solid Supported α-Acilthiones

Abstract

A solid supported dienic α,α′-dioxothione, obtained from the corresponding resin-linked β-chetoester, is able to react with vinyl ethers to give chemo- and regiospecifically the expected oxathiin cycloadducts. Trans-esterification allowed a quantitative and very clean cleavage of the products from the solid support.     

Modelling flow enhancement in nanochannels: Viscosity and slippage

With a large number of experimental and modelling papers reporting higher than expected liquid flow rates in both hydrophobic and hydrophilic nanochannels published in the last few years, there is a need to develop a coherent theoretical framework to explain these phenomena. In this work we will introduce a complete modelling and present a comparison between experimental data and predicted flows, showing good agreement.     

3,6-Bis(dimethylamino)-10-propylacridinium iodide

In the title compound, C₂₀H₂₆N₃⁺·I⁻, the acridinium moiety shows mirror symmetry about the central C—N vector. The fused tricyclic system is only approximately planar and the geometry is affected by the presence of both di­methyl­amino groups and the propyl substitution at the central N atom. The propyl chain adopts an extended trans conformation and the plane through the chain C atoms is perpendicular to the mean plane through the rings. The I⁻ ion is involved in short-range hydrogen-bonding interactions with two centrosymmetrically related cations via three activated acridinium C atoms. Stacks of acridinium cations propagate through the crystal along the c direction. The ring overlap is partial, but the di­methyl­amino groups also participate in the stacking.     

Toward sustainable and effective HER electrocatalysts: Strategies for the basal plane site activation of transition metal dichalcogenides

Due to their low cost and overall sustainability, transition metal dichalcogenides (TMDCs) are potential alternatives to noble metals as catalysts to produce green hydrogen. A promising route to improve their performances consists of activating their basal plane, both increasing the number of active sites or their specific activity. This can be accomplished by exploiting point defects, in-plane boundaries and strain. In particular, single atom adsorbed or incorporated into TMDCs have shown remarkable results in electrochemical half-cell tests. Topological curvature or grain boundaries (and related defects) can also be used to further boost the performances. A crucial point for the application of such strategies is related to the development of cost effective and sustainable methods for the scale-up of synthetic protocols.     

A Roman bronze statuette with gilded silver mask from Sardinia: an EDXRF study

A Roman bronze statuette from the 2nd Century BC was recovered from a nuragic sanctuary close to Florinas, in the north of Sardinia. The facial portion of the statuette is covered by a silver mask, partially gilded and attached to the bronze by tin-lead welding. The silver mask was carefully analyzed by portable energy-dispersive X-ray fluorescence (EDXRF), a non-destructive and non-invasive method. The aim of the analysis was to reconstruct the layered structure of the silver gilt mask, and to determine homogeneity and thickness of the gold, silver and lead–tin sheets. This is possible by using the internal ratio of the X-ray lines, i.e. starting from the surface, Au (Lα/Lβ), Ag (Kα/Kβ), Au-Lα/Ag-Kα and Pb (Lα/Lβ).The results were compared with those obtained with simulated X-ray spectra, obtained both experimentally and by using the Monte Carlo simulation technique.     

Binding to DPF-motif by the POB1 EH domain is responsible for POB1-Eps15 interaction

Background  

Eps15 homology (EH) domains are protein interaction modules binding to peptides containing Asn-Pro-Phe (NPF) motifs and mediating critical events during endocytosis and signal transduction. The EH domain of POB1 associates with Eps15, a protein characterized by a striking string of DPF triplets, 15 in human and 13 in mouse Eps15, at the C-terminus and lacking the typical EH-binding NPF motif.